bn  = nn.BatchNorm2d(num_features=3,# 表示特征通道数
                        eps=1e-5,      # 默认为1e-5
                        momentum= 0.1, # 默认为0.1
                        affine= True, # 默认为True
                        track_running_stats = True# 默认为True
                       )
y = bn(x)
print('running_mean=', bn.running_mean)
print('running_var=', bn.running_var)
print('weight=', bn.weight) # gamma 
print('bias=', bn.bias)     # beta
print(y) 
